INT 21h AH=41h removes a file from its directory. The name is ASCIIZ and may include a drive and a path. It must name one file: this function takes no wildcards, so to delete *.TMP a program finds each match with INT 21h AH=4Eh / 4Fh and deletes it by name.

AXMeaning
02hfile not found
03hpath not found: a directory in the name does not exist
05haccess denied: the file is read-only, the name is a directory (those go with INT 21h AH=3Ah) or a device
prints two lines: "first delete: ok" and "second delete: CF = 1, there is nothing left to delete"
MOV     AH, 3Ch           ; DOS: create TEST.TXT
XOR     CX, CX            ; CX = 0: normal attributes
MOV     DX, OFFSET FNAME
INT     21h
CALL    CHECK             ; stop if CF = 1
MOV     BX, AX            ; BX = the handle
MOV     AH, 3Eh           ; close it first
INT     21h
MOV     DX, OFFSET M1
MOV     AH, 09h           ; DOS: print the string at DS:DX
INT     21h
MOV     AH, 41h           ; DOS: delete TEST.TXT
MOV     DX, OFFSET FNAME
INT     21h
CALL    REPORT
MOV     DX, OFFSET M2
MOV     AH, 09h           ; DOS: print the string at DS:DX
INT     21h
MOV     AH, 41h           ; the same name again
MOV     DX, OFFSET FNAME
INT     21h
MOV     DX, OFFSET GONE1  ; CF = 1: nothing by that name
JC      SHOW1
MOV     DX, OFFSET ODD1
SHOW1:
MOV     AH, 09h
INT     21h
 
FNAME   DB      "TEST.TXT", 0
M1      DB      "first delete: $"
M2      DB      "second delete: $"
GONE1   DB      "CF = 1, there is nothing left to delete", 13, 10, "$"
ODD1    DB      "CF = 0?", 13, 10, "$"
CRLF    DB      13, 10, "$"
CHECK   PROC    NEAR      ; CF = 1: print the error code in AL and exit
JNC     CHECK1
PUSH    AX
MOV     DX, OFFSET FAILMSG
MOV     AH, 09h
INT     21h
POP     AX
CALL    PHEXB
MOV     AX, 4C01h         ; exit with code 1
INT     21h
CHECK1:
RET
CHECK   ENDP
FAILMSG DB      "failed: error $"
REPORT  PROC    NEAR      ; CF = 0: "ok"; CF = 1: "error" and AL
JC      REPORT1
MOV     DX, OFFSET OKMSG
MOV     AH, 09h
INT     21h
RET
REPORT1:
PUSH    AX
MOV     DX, OFFSET ERRMSG
MOV     AH, 09h
INT     21h
POP     AX
CALL    PHEXB             ; the error code
MOV     DX, OFFSET CRLF
MOV     AH, 09h
INT     21h
RET
REPORT  ENDP
OKMSG   DB      "ok", 13, 10, "$"
ERRMSG  DB      "error $"
PHEXB   PROC    NEAR      ; print AL as two hex digits
PUSH    CX
PUSH    DX
MOV     DH, AL            ; keep the byte
MOV     CL, 4
SHR     AL, CL            ; the high digit first
MOV     CX, 2
PHEXB1:
AND     AL, 0Fh
ADD     AL, "0"
CMP     AL, "9"
JBE     PHEXB2
ADD     AL, 7             ; 10..15 -> "A".."F"
PHEXB2:
MOV     DL, AL
MOV     AH, 02h           ; DOS: print DL
INT     21h
MOV     AL, DH            ; then the low digit
LOOP    PHEXB1
POP     DX
POP     CX
RET
PHEXB   ENDP

On MS-DOS the second delete returns AX = 02h, file not found. DOSBox-X, on a host folder, can leave an earlier access-denied code in AX instead, which is why the example tests only CF.

What happens on a FAT disk: DOS marks the directory entry free by overwriting the first character of the name with E5h, and frees the file's clusters in the FAT. The data stays on the disk until something reuses those clusters, which is how UNDELETE can bring a file back if you are quick.

Pitfalls

Close a file before deleting it. Without SHARE, MS-DOS deletes an open file without complaint, and later writes through the stale handle land in clusters that now belong to nobody, or to another file. DOSBox-X, on a host folder, closes the program's handles to the file and then deletes it. A read-only file must have its attribute cleared with INT 21h AH=43h first.